Selective electric signaling.



A H. NICHOLSON.

SELECTIVE ELECTRIC SIGNALING.

APPLICATION FILED FEB. 20, 1908.

Patented Jan. 12, 1909.

WITNESSES TN! NORRIS PITER: co., wnsumuwu, a c4 UNITED STATES PATENT OFFICE.

ARTHUR HAROLD NICHOLSON, OF WENDOVER, ENGLAND.

SELECTIVE ELECTRIC SIGNALING.

To all whom it may concern:

Be it known that I, ARTHUR HAROLD NIoHoLsoN, a subject of the King of Great Britain, residing at 5 Chiltern road, Vendover, in the county of Buckingham, England, electrical engineer, have invented certain new and useful Improvements in Selective Electric Signaling, of which the following is a specification.

In selective signaling of the kind described in specification to United States Patent No. 743,512, a non-polarized relay may be used, the function of which is to attract its armature in whichever direction it is traversed by the energizing current. In practice such a relay is apt to be uncertain in its action owing to the impossibility of avoiding residual magnetism in the core of the electromagnet; thus it may happen that having been traversed by a powerful current in one direction the armature remains attracted so that an immediately succeeding current in the opposite direction, neutralizing the residual magnetism, throws ofi' the armature, producing the reverse effect to that intended. Reliable relays of this kind have, indeed, been constructed, but the air gap necessitated makes them insufficiently sensitive to the limited battery power available for commercial omnibus telephone calling.

By my invention I make a polarized relay fulfil the functions of the non-polarized relay by providing it with two relay contacts in series with each other so that if either contact is interrupted the circuit is broken.

The accompanying diagram illustrates the application of such a relay, it being premised that it has been customary to make selective signaling relays with two cores, one polarized and the other non-polarized, and that for the proper operation of the relay one of the cores has two windings, while the other has one; whether the relay will close the local circuit or not depends on the di rection of the currents through the windings.

In the diagram there are two polarized relays, a fulfilling the functions of the polarized core in the known construction and b that of the non-polarized core. Both are Specification of Letters Patent.

Application filed February 20, 1908.

Patented Jan. 12, 1909.

Serial No. 416,816.

shown as having two windings, but this is merely to make the apparatus applicable to any station, and in use one of the four windings remains idle.

According to the invention the armature of the relay 6 has two contacts, 0, d in series with each other in the local circuit, which includes the contact 6 of the relay a the bell f and the battery 9. The type of relay illustrated is a known form in which the core is suspended by a spring and itself plays the part of an armature.

When the relay Z) is without current or is traversed by currents in opposite directions it remains inactive, that is to say the light springs 7L 2' carried by its armature remain against contacts 0 (Z respectively and whether the local circuit is closed or not depends upon whether current traverses relay a in proper direction for bringing its spring in against the contact a. If, however, a single current traverses relay 6 in either direction its armature is attracted and one of the springs h z is withdrawn from its contact; the local circuit cannot now be closed whatever happens at relay a.

Z is a rigid bar acting as a stop.

Having thus described the nature of this invention and the best means I know of carrying the same into practical efl'ect, I claim In selective electric signaling, means for controlling a local circuit comprising a polarized relay having a single contact normally open and adapted to be closed by currents energizing the relay, and a doubly wound polarized relay having a pair of contacts in series with the first contact in the local circuit, said pair of contacts being normally closed and adapted to be actuated to break the circuit by currents energizing the said second polarized relay.

In testimony whereof I have signed my name to this specification in the presence of two subscribing wltnesses.

ARTHUR HAROLD NICHOLSON. I

Witnesses:

JOSEPH MILLARD, WALTER J. SKERTEN. 

